New "fracture-label" techniques recently developed in our laboratory are used to show the distribution and partition of glycoproteins in intracellular membranes of secretory as well as non-secretory cells. We define the existence of two membrane types: Those with fully glycosylated sialoglycoproteins are intensely labelled by wheat germ agglutinin/colloidal gold complexes; other membranes, which are not labelled by WGA but are intensely labelled by Concanavalin A/colloidal gold and their (i.e. their glycoproteins are not sialidated). Our study shows, for the first time and at high resolution (better than 20 nm) the pattern of intracellular distribution of membrane glycoproteins in eukaryotic cells.